The present invention relates generally to a method of differentiating tires in a vehicle including a tire pressure monitoring system by communicating tire identification information in a sensor to a receiver to identify the location of the tires.
It is often desirable to differentiate between the lower pressure front tires and the higher pressure rear tires on certain vehicles, especially trucks. The front tires generally are at a pressure of about 35 psi. The desired pressure of the rear tires varies depending on the load of the vehicle, but is generally in the range of 60-75 psi. As the rear tires are at a higher pressure, it is important to monitor them to ensure that the high pressure is maintained.
Tire pressure monitoring systems (TPMS) have been employed to monitor the pressure in the tires. In one prior system, the vehicle operator is alerted when a sensor in the tire detects that the pressure in the tire drops below a predetermined level. Each sensor includes an electronic code identifier. When the sensor detects that the pressure in the tire drops below the predetermined level, the sensor sends a signal to a receiver, displaying the electronic code identifier and alerting the operator of the problem. A drawback to this prior system is that even if the identity of the problem tire is known, the location of the problem tire is not as the electronic code identifier only identifies the tire, not the tire location. Commonly, after being alerted to a problem, the operator determines the location of the problem tire by manual inspection.
Pressure responsive switches have also been utilized to monitor tire pressure and to indicate to an operator when the tire pressure is too high to too low. In one prior system, a switch is activated when the tire pressure is too high or too low, indicating the pressure is not optimal. However, even if the operator is made aware of the problem, the operator does not know the location of the tire.
A tire differentiating system is employed to differentiate tires in a vehicle. In a first example, each tire includes a sensor which communicates with a receiver to differentiate the front tires from the rear tires. When a tire is inflated above a high threshold pressure, a flag bit is stored in the sensor. As only the rear tires are inflated to a pressure greater than the high threshold pressure, only the rear tires have a flag bit.
If a sensor with a flag bit detects that the tire pressure drops below a low pressure threshold, a warning algorithm is initiated to warn the driver of the low pressure condition. As the front tires never reach a pressure high enough to retain the flag bit in the sensor, a pressure drop below the low pressure threshold in the front tires will not initiate the warning algorithm. The flag bit is permanently retained in the sensor until reset by reducing the pressure in the tire to zero.
A second example of the invention differentiates all of the tires in a vehicle. The sensor is a transceiver with a RF detector circuit. An identification code is stored in each transceiver and includes information regarding tire size, material, and rim size. A RF transmitter having an antenna is proximate to each of the tires in the wheel well.
To differentiate the tires, the receiver sends a RF signal to one of the RF transmitters in a tire in a known location. After receiving the signal, the RF transmitter generates a RF signal which is sent to the corresponding transceiver in the tire. As the transmitter is proximate to the transceiver, only the desired transceiver will receive the RF signal. After receiving the signal, the transceiver then sends a return signal including the identification code to the receiver. After recognizing the identification code, the receiver relates the identification code to the location. This process is repeated for each tire location to identify the tire in each location.
These and other features of the present invention will be best understood from the following specification and drawings.